1. Technology Area
The invention relates to printhead mounting arrangements for a serial printer and more specifically to printhead mounting arrangements for serial printers that employ a printing ribbon that wraps around the printhead.
2. Art Statement
In order to provide print line visibility with a printing system that uses a ribbon, the ribbon is typically wrapped around the printhead so as to avoid obscuring the printed characters on the trailing side (trailing respective of the forward direction for printing) of the printhead. One characteristic of this arrangement is that the ribbon tension forces tug on the printhead and tend to pull it away from the medium receiving the printing marks. This pulling force tends to vary and creates a problem when using a delicate printhead, such as a printhead composed of fine electrodes, because of the increased printhead force required to assure continuous intimate printhead-to-ribbon and ribbon-to-receiving medium contact. Since ribbon supply arrangements generally involve several ribbon path direction changes and some contact with ribbon guides, significant ribbon tension variations are difficult to avoid.
As alluded to above, one way to eliminate the effects of such ribbon tension variations on printing pressure is to maintain the ribbon path parallel to the print line. If the ribbon does not wrap around the printhead, little if any ribbon force is applied to the head. But with such an arrangement, the ribbon blocks the operator's view of the printed characters as a line is printed.
A pattern formed on the operator's side of the ribbon (see U.S. Pat. No. 4,195,937) can serve as a substitute for a view of the line as it is printed. But this is not a feasible alternative for printing systems that do not cause the side of the ribbon away from the receiving medium to become marked.